Down here in SA we use flashers for hunting many pelagic species. Yellowtail just love them and for me it's must have when targeting them.
My standard flasher is a Rob Allen spinner flasher. Simple, robust and effective flasher. The action of the float in the swell pulls the flasher up and down which in turn spins the stainless flashers. Below the spinner flasher in action:
I've recently started using a combination of two of Rob Allen's flashers. The bait ball flasher at the top and the spinner flasher at the bottom. I like this combo as it has a lot of different type of actions to it, it's compact so saves space on the boat and it's easy to roll up after a drift then redeploy after at the top or the drift. Just to liven things up I also add a little disco ball to the flasher to simulate the flashing sides of bait fish in a bait ball.
Combination flasher:
Some of my dive buddies use different flashers. Below is a pom-pom flasher which essentially is silver plastic bag cut to shreds. When under water it's remarkable how closely this flasher resembles a tightly packed bait ball of small fish and it's not strange to see this flasher completely engulfed by bottom fish.
Pop-pom under water:
Another effective item to add is a rattle to the end of your flasher. Pictured below is a dive buddy giving his rattle a good shake to call fish in.
As can be seen in this photo, sharks love flashers. Although they work well, I steer clear of the ladder type flashers as sharks will go for them and invariably get stuck in between the slats then swim away with the flasher and float.
As for burly or chum. When hunting Tuna it's the best way to bring these erratic swimmers up close enough to spear them. We create a chum trail by cutting sardines into sections and sporadically throwing theses pieces as we drift in the current / wind. This trail may extend up to a few kilometres if we keep chumming long enough. Any tuna that crosses the trail then eat their way to the boat where we hopefully meet them. In the area where we target Tuna (usually 20 - 40 nautical miles from shore) sharks are normally not a problem as it's mostly Blue sharks and once in a while a Mako we may encounter. Closer to the shore we normally will not make use of chum, in fact we make a concise effort to get fish that has been shot out of the water as soon a possible as to not entice any toothy critters.
Below sardine pieces can be seen seen floating down the chum trail as I wait for Tuna to make an appearance: